To fully understand the invention, it is necessary to consider the anatomy and physiology of the lacrimal system. The orbital portion of the lacrimal gland is located in the superotemporal orbit and produces the aqueous layer of the tear film. Ductules from the orbital portion of the lacrimal gland pass through the adjacent palpebral lacrimal gland to empty in the superior conjunctival cul-de-sac. Smaller accessory lacrimal glands in the upper and lower lids also contribute to tear production The tears bathe the surface of the eye and then drain into the puncta and canaliculi in the medial upper and lower lids. The tears flow from the canaliculi into the lacrimal sac down the nasolacrimal duct into the nose.
The nasolacrimal duct can become obstructed on either a congenital or acquired basis When the nasolacrimal duct becomes obstructed, tears can no longer drain from the surface of the eye through the lacrimal system into the nose. The tears well up over the eye and spill over the lids onto the face. The patient has to constantly dab the eye with a tissue. In addition, tears stagnate in the lacrimal sac, bacteria multiply, and in many cases the lacrimal sac becomes infected (dacryocystitis). Dacryocystitis causes the lacrimal sac to become swollen, red and painful. Pus exudes from the sac and constantly covers the eye. In time, the dacryocystitis does not respond to antibiotics and surgery becomes necessary. At present, there is no medical therapy for acquired nasolacrimal duct obstruction other than antibiotics to temporarily suppress infection.
The condition can, however, be corrected surgically. Dacryocystorhinostomy (DCR) is the surgery required to correct nasolacrimal duct obstruction. In a DCR, a new opening (ostium) is created between the lacrimal sac and the nose. This allows tears to flow from the lacrimal sac through the DCR ostium into the nose. An external or incisional DCR required an incision on the side of the nose. In an open DCR, the surgeon creates a large 17 mm plus diameter opening in the bone and nasal muscosa. This procedure has significant morbidity, a prolonged recovery, and the threat of scarring and hemorrhage. In contrast, an endoscopic DCR has much less morbidity, no incision, and a quick recovery time. An endoscopic DCR may be performed using a balloon catheter, a laser, or traditional surgical instruments. A laser endoscopic DCR requires expensive and time-consuming lasers, and has a low success rate. An endoscopic DCR with traditional instruments places the eye and surrounding structures at risk because tissue is removed from the lacrimal sac and lateral nasal wall, with the instruments in the nasal cavity going toward the eye and orbit. Bleeding and edema may make it difficult to identify the relevant structures.
It has been found that a balloon catheter DCR is a much safer and cheaper form of DCR than a laser or an endoscopic DCR with traditional surgical instruments. The balloon catheter is positioned so that it extends from the lacrimal sac through the ostium and extends into the nose. Since the balloon DCR ostium is created by dilatation, rather than by excision or laser energy, there is no threat to the surrounding ocular and orbital structures, and there is less tissue trauma.
As shown in U.S. Pat. Nos. 5,021,043 and 5,169,043, I have previously co-invented balloon catheters for use in the lacrimal system. These balloon catheters are inserted from the eye through the small diameter (about 0.5 mm) delicate punctum and canaliculus into the lacrimal sac extending through the planned ostium into the nose. The deflated profile diameter of the balloon catheter must be very small in order to be pushed through, and avoid damage to, the small diameter and delicate canaliculus. The need for such a small deflated diameter limits the inflated diameter of the balloon to 5 mm. However, a 5 mm diameter ostium is much smaller than the 17 mm plus diameter ostium of an external DCR and leads to a higher stenosis rate of the balloon DCR ostium after surgery. A larger diameter balloon would create a larger-diameter ostium and lead to a higher surgical success rate.
This led to the concept disclosed beginning at column 7, line 29, and FIG. 4 of the U.S. Pat. No. 5,021,043 patent and beginning at column 8, line 34, and FIG. 4 of the U.S. Pat. No. 5,169,386 patent that a dilation catheter be introduced transnasally when a larger-diameter balloon is required. However, as taught in these patents, the dilation catheter is inserted over a guide wire. Although this technique is useful, it involves a number of time-consuming steps, including the insertion of a guide wire through the lacrimal system, and then separately advancing the balloon catheter over the guide wire. This technique requires the placement of a guide wire through the canaliculi into the nose. The surgeon then reaches up the nose with a hemostat or other instrument to grasp the guide wire and pull it out of the external naris of the nose. A flexible balloon catheter is then passed up the nose over the guide wire and through the lateral nasal wall into the lacrimal sac, or up the nasolacrimal duct into the lacrimal sac. However, there are problems with this method. First, there may be difficulty locating and grasping the guide wire in the nose, especially if even mild bleeding is present. The guide wire may pass posteriorly into the throat (pharynx) rather than in the direction of the external naris. There is often resistance to pulling the balloon from the nasal cavity into the lacrimal sac and considerable force is required to pull the balloon and guide wire into the lacrimal sac. This pull on the guide wire can cause it to slice through the delicate canaliculi, which may lead to secondary fibrosis and obstruction of the canaliculi after surgery.
The U.S. Pat. No. 5,169,386 patent also discloses an alternative dilation catheter, which does not use a guide wire, but there is no suggestion that this catheter be inserted transnasally. The catheter is constructed to simulate a standard ophthalmic probe in stiffness, in terms of both column strength and resistance to lateral bending, with sufficient flexibility to enable it to conform to the contours of the lacrimal system. The catheter, as provided, is initially straight, but the catheter may be bent between 0°–30° to simulate the curvature of an ophthalmic probe. A curve retention element is inserted in the catheter to retain the curved shape and to increase the columnar and flexural stiffness of the distal portion of the catheter to enhance its ability to be forced through a constricted portion of the lacrimal system. The catheter is formed of a stainless steel hypotube having an outer diameter of 0.022″ and an inner diameter of 0.017″.
This catheter is not suitable for transnasal insertion. The tube does not have sufficient stiffness and column strength to enable the deflated balloon catheter to be pushed from the nasal cavity through a small, tight opening in the lateral nasal wall and lacrimal fossa into the lacrimal sac. Moreover, the bent distal portion is not angled to a degree necessary for ready insertion through the opening.